Computational and Experimental Studies of Regioselective S<sub>N</sub>Ar Halide Exchange (Halex) Reactions of Pentachloropyridine
作者:Robert D. J. Froese、Gregory T. Whiteker、Thomas H. Peterson、Daniel J. Arriola、James M. Renga、Justin W. Shearer
DOI:10.1021/acs.joc.6b01656
日期:2016.11.18
important thermodynamic factor which controls regioselectivity in this system is the weak C2–Cl bond. The differences between ΔH° values of chlorofluoropyridines can be explained by a combination of three factors: (1) the number of fluorine atoms in the molecule, (2) the number of fluorine atoms at the C2 and C6 positions, and (3) the number of pairs of fluorine atoms which are ortho to one another.
Chromium oxide is a good catalyst for scrambling halogens among polyhaloaromatic compounds. Chloropentafluorobenzene and bromopentafluorobenzene disproportionate to hexafluorobenzene and the respective tetrafluorodihalobenzenes. Pentachloro- and pentafluoropyridines produce pyridines with intermediate numbers of both types of halogens. Cyano, trifluoromethyl and a single hydrogen can be present on the aromatic rings without interfering with the chemistry.
Substitution of chlorine by fluorine in chloroaromatic compounds by the action of potassium and cesium fluorides in graphite
作者:V. V. Aksenov、V. M. Vlasov、V. I. Danilkin、O. Yu. Naumova、P. P. Rodionov、V. S. Chertok、G. N. Shnitko、G. G. Yakobson